KDR and meningioma: Our previous study with a limited amount of patients and a short follow-up investigating vascular endothelial growth factor (VEGF) and its two receptors, vascular endothelial growth factor receptor (VEGFR)1 (flt-1) and VEGFR-2 (flt-1/KDR), demonstrated heterogeneous expression levels but no influence on progression-free survival (PFS) or overall survival (OAS) in WHO grade II and III meningiomas (Baumgarten et al. 2013).